This paper evaluated the ecological security comprehensive index of Shanxi Province from 2000 to 2018, based on the "Pressure-State-Response"(PSR) model. It also analyzed its temporal and spatial evolution characteristics. The Dagum Gini coefficient was used to measure the regional differences and sources of the ecological security level, while the spatial measurement model was used to explore the influencing factors. The results show that the overall trend of ecological comprehensive index is rising, the ecological environment has a big improvement but the ecological security level is relatively low. At different administrative city scales, the increase of comprehensive index of ecological security decreases with the decrease of the administrative unit scales. The spatial distribution of county ecological security shows a band distribution. It presents a disequilibrium pattern decreasing from the middle to the north and south. The degree of spatial agglomeration is increasing. The level ecological security at county scale is spatially unbalanced, but the unbalance is declining. The regional difference is the main source of spatial overall differences. It presents obviously spatial spillover effect. Economic scale, population density, urbanization rate, NDVI and elevation are the key factors affecting the spatial evolution of county ecological security. The spatial characteristics of ecological security level has scale effect. The larger the research scale, the greater the scale effect. The balance between the integrity and sustainability of ecosystem functions needs to be maintained on a larger scale. The evolution of ecological security level at county scale has path dependence. It is necessary to innovate development models to get rid of path dependence, and achieve the path breakthrough. Maintaining a balance between the relatively stable state of the ecosystem and the sustained development of human society and economy on the basis of economic development is the key to promote the level of regional ecological security and maintain the harmonious coexistence between human and nature.